Vehicle drive device

Abstract

A control device that controls an internal combustion engine, a first rotary electric machine, a first engagement device, and a second engagement device performing first transition control when transition is performed from a first mode to a second mode. The first transition control includes first control, second control, and third control. The first control is control in which the second engagement device that connects and disconnects power transmission between two rotary elements selected from among three rotary elements of a distribution differential gear mechanism is changed from an engaged state to a disengaged state while a third engagement device of a transmission mechanism is maintained in an engaged state. The second control controls a rotational speed of the first rotary element to is changed from a disengaged state to an engaged state and the internal combustion engine is started by using drive power transmitted from the first rotary electric.

The invention claimed is: 
     
       1. A vehicle drive device comprising:
 an input member drivingly coupled to an internal combustion engine; 
 a first output member drivingly coupled to a first wheel; 
 a first rotary electric machine including a rotor; 
 a distribution differential gear mechanism including a first rotary element, a second rotary element, and a third rotary element, the first rotary element being drivingly coupled to the input member, the third rotary element being drivingly coupled to the rotor; 
 a transmission mechanism that performs at least power transmission between the second rotary element and the first output member; 
 a first engagement device that connects and disconnects power transmission between the input member and the first rotary element; 
 a second engagement device that connects and disconnects power transmission between two rotary elements selected from among three rotary elements that are the first rotary element, the second rotary element, and the third rotary element; and 
 a control device that controls the internal combustion engine, the first rotary electric machine, the first engagement device, and the second engagement device, 
 the transmission mechanism including a third engagement device that connects and disconnects the power transmission between the second rotary element and the first output member, 
 wherein 
 the vehicle drive device has a first mode and a second mode as operation modes, 
 in the first mode, the first engagement device is brought into a disengaged state, the second engagement device is brought into an engaged state, the third engagement device is brought into an engaged state, and the internal combustion engine is brought into a stopped state of not outputting drive power, and drive power of the first rotary electric machine is transmitted to the first output member, 
 in the second mode, the first engagement device is brought into an engaged state, the second engagement device is brought into a disengaged state, and the third engagement device is brought into an engaged state, and drive power of the internal combustion engine and the first rotary electric machine is transmitted to the first output member, 
 the control device is allowed to perform a first transition control when transition to the second mode from the first mode is performed, and 
 the first transition control includes: 
 a first control in which the second engagement device is changed from an engaged state to a disengaged state while the third engagement device is maintained in an engaged state; 
 a second control in which, after the first control, a rotational speed of the rotor is controlled to cause a rotational speed of the first rotary element to approach a target rotational speed; and 
 a third control in which, after the second control, the first engagement device is changed from a disengaged state to an engaged state and the internal combustion engine is started by using drive power transmitted from the first rotary electric machine to the internal combustion engine via the first engagement device. 
 
     
     
       2. The vehicle drive device according to  claim 1 ,
 wherein the first engagement device is a friction engagement device including a direct-coupling engaged state and a slip engaged state as engaged states, 
 wherein the target rotational speed is the rotational speed of the first rotary element determined based on a rotational speed of the internal combustion engine for the internal combustion engine to output drive power to be required after transition to the second mode, and 
 wherein, in the third control, during an engagement operation in which the first engagement device is changed from the disengaged state to the direct-coupling engaged state through the slip engaged state, the control device causes the rotational speed of the internal combustion engine to increase to start the internal combustion engine, by using drive power transmitted from the first rotary electric machine to the internal combustion engine via the first engagement device in the slip engaged state. 
 
     
     
       3. The vehicle drive device according to  claim 1 ,
 wherein the target rotational speed is zero, 
 wherein the rotational speed of the first rotary element determined based on the rotational speed of the internal combustion engine for the internal combustion engine to output drive power to be required after transition to the second mode is set as a post-transition target rotational speed, and 
 wherein, in the third control, after the first engagement device is changed from a disengaged state to a direct-coupling engaged state, the control device controls the rotational speed of the rotor to cause the rotational speed of the first rotary element to approach the post-transition target rotational speed, and causes a rotational speed of the internal combustion engine to increase to start the internal combustion engine, by using drive power transmitted from the first rotary electric machine to the internal combustion engine via the first engagement device in the direct-coupling engaged state. 
 
     
     
       4. The vehicle drive device according to  claim 1 , further comprising a second rotary electric machine that is drivingly coupled to, not via the first output member, a second output member drivingly coupled to a second wheel different from the first wheel, or that is drivingly coupled to the first output member on a side of the first output member with respect to the third engagement device in a power transmission path between the second rotary element and the first output member,
 wherein 
 while the first transition control is performed, the control device performs drive power compensation control in which the second rotary electric machine is caused to output drive power to compensate for fluctuation in drive power, from the first rotary electric machine and the internal combustion engine, transmitted to the first output member via the transmission mechanism. 
 
     
     
       5. The vehicle drive device according to  claim 4 ,
 wherein the control device is allowed to selectively perform the first transition control and a second transition control when transition to the second mode from the first mode is performed, 
 wherein the second transition control includes: 
 a fourth control in which the third engagement device is changed from an engaged state to a disengaged state while the second engagement device is maintained in an engaged state; 
 a fifth control in which, after the fourth control, the rotational speed of the rotor is controlled to cause the rotational speed of the first rotary element to approach the target rotational speed; 
 a sixth control in which, after the fifth control, the first engagement device is changed from a disengaged state to an engaged state and the internal combustion engine is started by using drive power transmitted from the first rotary electric machine to the internal combustion engine via the first engagement device; and 
 a seventh control in which, after the sixth control, the third engagement device is changed from a disengaged state to an engaged state and the second engagement device is changed from an engaged state to a disengaged state, and 
 wherein the control device performs the first transition control when surplus drive power that is a difference between drive power being output by the second rotary electric machine and upper-limit drive power outputtable by the second rotary electric machine is equal to or larger than required drive power that is drive power required for performing the drive power compensation control, and performs the second transition control when the surplus drive power is smaller than the required drive power.